The present disclosure relates to electrostatic charge image developing toners.
In order to save on energy consumption or to achieve size reduction in image forming apparatuses using toner, it is desirable that the toner has excellent fixability at low temperature. The use of such toner can achieve suitable fixability, while suppressing heating of a fixing roller. However, the toner excellent in fixability at low temperature includes at least one of a binder resin having a low melting point or glass transition point and a releasing agent having a low melting point in many cases. Such the toner tends to aggregate in high temperature storage. Aggregation of the toner may tend to cause image defect or fogging in image formation. The image defect might be caused due to adhesion of the toner to a development sleeve or a photosensitive drum. The fogging might be caused due to charge failure of the toner.
In view of the foregoing, in order to improve the fixability of the toner in a wide range of temperature, to enhance the preservation stability of the toner at high temperature, or to improve the blocking resistance of the toner, a toner having a core-shell structure has been proposed. Core particles of such the toner are each covered with a shell layer. In some toner having a core-shell structure, the core particles include a binder resin with a low melting point, and the glass transition point (Tg) of a resin forming the shell layer is higher than the glass transition point (Tg) of the binder reins of the core particles. Further, an intermediate layer and the shell layer are formed on the surface of each core particle. The intermediate layer includes wax. The shell layer includes crystalline polyester resin with a softening point of 60° C. or higher and 120° C. or lower at a rate of 70% by mass or higher and 100% by mass or lower.